Newbie question on prop setup...

[mitsugsx813]

Im trying to finish up my boat build. I have a 13' baja style hull i just finished up with a late 70's 70hp merc. Props pretty beat up from previous owner of the motor. Was wondering if anyone could help me with a basic guideline for size and pitch. Whats better torque wise? Which would be better for speed/rev limit? Any advice will help...

http://i57.photobucket.com/albums/g222/mitsugsx813/Brandon-20110916-000841.jpg

http://i57.photobucket.com/albums/g222/mitsugsx813/IMG-20110813-000301-1.jpg

[David]

18" baby chopper?

[200VEGAS]

about 5600-6000rpm max? probably not dual cable steering, is it? and no powewr trim?

[mitsugsx813]

Single steering cable and it did have power trim, but my pressure lines blew and im havin a hard time finding new ones. Im getting ready to store it and want to start looking for some go fast parts for next spring...

[terry taylor]

I would say your boat is a 13 ft. checkmate , I don,t know about a merc. prop.

[David]

I got an 18" chopper with my old Voo Doo/70 Nissan which was a similar size/power hull. Take off was lousy of course, with lots of revs and no speed. Once on a plane, it was a good all round prop. If you have 1.64 gears the 18 will be enough pitch.

[mitsugsx813]

Thanks!

[200VEGAS]

i think wildman here on the board has a little experience with that hull. he put a 225 promax on it. and then went to like a 60 merc

[mitsugsx813]

What kind of props should i look for? i hear chopper and cleaver alot. Should i go aluminum or stainless?

[200VEGAS]

stainless and no cleavers they are for tunnel boats mostly. choppers are great. you need a high rake round ear cupped stainless of about 18 or 20 pitch, to try to set an rpm baseline and go from there. try to find out your gear ratio with internet search. Take a couple pics of your motor-hull transom side up close. i dont think omc props are for you as they have a longer hub and different spline(I THINK). I wonder if the small gearcase laser style props would work hub wise. maybe someone else has that info. and you will need that power trim line replaced. look on <misc parts>for a replacement and use a light weight motor oil to refill it. i think like 20w. as far as the torque-speed prop question, a pitch at the top of your recomended rpm range at wot will be your torque type prop, and one at the lower range will be your faster prop top speed wise. the trim is really going to effect your rpm, so i would start by fixing that. think of the pitch change as putting a lower gear ratio axle in your race car. only a lot easier

[mitsugsx813]

Thanks again for all the help! Really nice to find people that have a clue of what there talking about...